The Russian mathematician and physicist Friedmann and the Belgian priest and physicist Lemaître were the first to consider non‐static world models in the framework of Einstein's general theory of relativity. Friedmann seemed to favour a periodic, oscillating cosmological model. His investigations were taken up by Russian cosmologists in the 1960s. They stated that the singularities present in many of the Friedmann‐Lemaître cosmological models seemed to be artificial and were ascribed to the assumption of a highly symmetric distribution of cosmic matter. Their disapproval of singularities seems to be in accord with Soviet ideological requirements during that time like atheism and dialectic materialism. They had to retract their statements after Hawking had proved his singularity theorems and after the microwave background had been discovered. Hawking followed the line of thought which was initiated by Lemaître in the early 1930s. Lemaître had combined for the first time quantum physics and relativistic cosmology and had developed his idea of the primeval atom, a beginning of the universe in a dense state with just one quantum containing the whole mass of the universe. Pope Pius XII brought together this primeval atom and God as the Creator of the universe and declared in 1951 that big bang cosmology is compatible with the Bible. Not surprisingly Hawking was awarded the Pius XI medal by the Vatican in 1975 for his contributions to big bang cosmology. 相似文献
A major advantage of satellite remote sensing is that the imagery acquired provides a synoptic view of the landscape. Thus, repeat coverage by the satellite on a regular basis permits the detection of changes in land‐cover over time. This study demonstrates the application of remote sensing technology to the monitoring of mining activities at the Athabasca Oil Sands region of Alberta, Canada. First, we describe the techniques used to match a time sequence of Landsat imagery, both spatially and spectrally, to ensure that the spectral changes through time are due to land‐cover variations. A series of spectral trajectories were then extracted to assess changes in land‐cover through time. Secondly, a land‐cover classification was produced from the baseline 1984 imagery and, using historic and future mine extents, the classification was analyzed to determine the proportion of each land‐cover type affected through development. Results of the analysis indicate that since 1984 there has been a larger reduction in mixedwood dense and broadleaf vegetation classes than mixedwood sparse or dense conifer stands in the area. Based on the delineations of mine‐site activity, the area of woodland and wetland habitat subject to development has increased from approximately 2,520 hectare (ha) in 1984 to 32,930 ha in 2005. 相似文献
Although the close association of word and image in medieval cartography is widely acknowledged, the significance of the relationship after the rediscovery of Ptolemy's Geography and throughout the Renaissance has been overlooked, despite Abraham Ortelius's choice of the term ‘Reader’ for users of the Theatrum orbis terrarum (1570). In this paper, the map of the world, which (as in Ptolemy's Geography) opens Ortelius's Theatrum, is analysed to show how Ortelius's concept of space was very different from Ptolemy's. Attention is drawn to the content of the texts on the map, to Ortelius's notion of geography as the eye of history, and to the importance in the Renaissance of the emblem as a conceit, or device, in the system of acquisition and transmission of knowledge. As in emblems, the words on Ortelius's map are not there to explain or to comment on what is seen but to give the image meaning; the purpose of the map is to invite contemplation of God's world. The map is contradictory, however; for Ortelius's accurate and up‐to‐date presentation of the physical world is qualified by a verbal statement that the world is ‘nothing’, a mere pinpoint in the immensity of the universe. It is concluded that Ortelius was not a geographer in the same way Ptolemy was, and that Ortelius was using geography as a philosopher and his world map as an illustration of his moral and religious thinking. 相似文献
Timber structures can be degraded during their life both by structural problems and by biological degradation factors like fungi and insects. The occurrence of those biodegradation agents could lead to a loss of their structural integrity, in the absence of appropriate maintenance. An early assessment of the decay is even more important when the wooden structures are part of historical buildings, in the interest of conservation of cultural heritage.
This article presents an application of microwave reflectometry for the in situ evaluation of timber structures. The measurement system allows detecting anomalies inside the material in a non-destructive and non-invasive manner.
The reflection coefficient is measured by means of a vector network analyzer (VNA) using a double-ridge antenna which transmits the continuous-wave (CW) microwave signal and receives the signal reflected by the material under investigation.
Measurements on laboratory models demonstrated the feasibility of the method. Results obtained on timber beam sections, compared with the findings of traditional investigation methodologies, demonstrate the potentiality of microwave reflectometry, suggesting its possible usefulness during the diagnostic phase as a non-invasive tool for preliminary screening. 相似文献
Photography as Science: In 1908 the English physicist Arthur Mason Worthington published A Study of Splashes, a treatise on the physical behaviour of falling drops. The photographic experiments were performed by means of an electric spark „in absolute darkness”︁. Worthington's experimental practice dealt with two different areas of knowledge production: an area the operator could perceive control from the outside and a corresponding black-box where the photographic recording itself took place. The paper discusses the epistemic challenges of this specific shift from imperceptible events to their photographic representations. It shows to what extent the information revealed by the photographic apparatus had to be converted, for it did not speak for itself. Thus, Worthington's work went beyond the classical dichotomy between objectivity and imagination. 相似文献